Heater temperature?

[dirtautoguy]

What’s everyone getting for heater temperatures? Yesterday on my way to work I noticed my heater didn’t seem as hot as it used to be (I usually have to turn it down or off before I get to work). It was warm for sure but not hot like it normally is. I measured the temps of the vents with a infrared sensor and got about 143f.

I have checked and the temperature does change with the dial so I think the blend doors are working. My engine temps were all normal. Water pump, radiator, radiator cap, thermostat are all fairly new.

Yesterday it was about 13f on my way to work and this morning it’s -3f and I had about the same result. It’s warm enough to be warm but it used to be that you about couldn’t stand It and would have to turn it off it would get the cab so hot.

I guess mostly im just wondering if there is a spec or general temp range I should see out of the vents before I go to crazy with this.

1996 rcsb 5.7

 

[Frank Enstein]

That may be as hot as it gets and is more noticeable due to the current temperature.

Double check the coolant level. Low coolant level can drop the heater output a bunch.

Check for air leaks. A tiny air leak will absolutely murder heat output. Think of the cab like a balloon that the heater keeps filled.

Somebody will likely pop up to answer your question better I am sure!

 

[dirtautoguy]

I did a little investigating today and didnt find a lot but I found a little.

my dads truck was handy so I did the same temperature test on his and found that he had very similar temps at about 140

I felt my heater hoses and found that the heater inlet was very warm I couldn't hold it. and found that the return line was pretty warm but I could leave my hand on it. the coolant is indeed still full.

I listened close on the way home for any air leaks and did some investigating around the weather stripping and such but didnt find anything obvious

maybe its not the truck and its just me getting older and wanting more heat! haha

 

[thinger2]

The infrared is not a real reiable way to test air temp.
They give you some feedback but they are wildly unreliable.
They are better suited for use on things like head and exhuast temps.
And the quality of those vary all over the place.
The better way is to get a chefs pocket size meat thermometer and stick it in the vents.
You will see some temp difference the further you get from the heater core.
If you see a massive difference that doesnt get better as you cycle through all of the heat settings and all of the vents?
Then you may have a blend door problem or leaking vent tubes.
That said, at 13 friggen degrees and a 195 or so thermostat and old with no heated seats?
I dont know what frozen arctic land you live in but I just got chilly from reading it.
These trucks run pretty cold and that is a lot of space to heat with dash vents.

 

[jfulton]

I am having the same issue, i have recently did a new water pump and 2 different thermostats and new coolant and bled the air out of the system, it doesn't heat up like it used to. I have a 1998 k1500 with a 5.7l. I used to have to shut the heat off and have to have a window open while plowing it was so hot. Even in single temps. I live in the northeast. I have been noticing since I did the new parts that my temp guage has been at the quarter mark and fluctuates around the quarter mark while I'm driving on top of it not heating up, its usually 2 lines above the quarter mark. I am putting new sensors in anyway but would be curious if its possible that both tstats were bad and have to find an oe part, or a bad rad cap or the fan clutch not working but can move back and forth with engine off. Any suggestions would be appreciative. Thanks

 

[Nad_Yvalhosert]

Have you thought about restricting the airflow through the radiator? Buses, Semis, Dump trucks, etc. usually have been seen with a canvas or leather cover around here.
As long as you monitor the temp gauge it would help.

I routinely watch my temp gauge when I'm on the highway with my snowplow. It sure blocks airflow at speed. I will admit I've hit 240° --- (talking to my wife will do that... you know, paying attention to her and not the gauges) --- before dropping the Unimount a few inches. Temp came down in a hurry!

 

[tinfoil_hat]

It could be the ducting. The seals around the duct joints rot out and the hot air bleeds out behind the dash. All the dashes I have ever removed were nightmare projects so I have not attempted it on my current truck.

 

[dirtautoguy]

Well I think maybe I found the issue.

Today while dropping my dogs off at daycare (my dads house) I let the truck idle. I talked to him for probably 10 minutes. When I got back in the truck it was hotter than the depths of hell!

The only real difference I can think of is the radiator. I replaced it a while ago with a all alluminum one that may also be a little bigger than stock? I don’t remember. Anyway i think that the truck is just running cool. I know it could be a thermostat issue but my temps don’t say there is a issue. It runs about 186-188 going down the highway in the winter and when I got in the cab after idling it was 194 according to my scangauge.

I may try putting some cardboard in the grille if we keep getting cold temps but it should start warming up now. I don’t think it’s going to stop working on me

 

[RichLo]

Less than 10* engine temp shouldn't cause that much of a difference in cab temp. I doubt cardboard in the radiator will do anything. But you did find a difference, maybe from sitting it was recirculating in-cab air. I have never been this far into the heater box before but I have heard that the foam around the heater core can disinigrate and go wifi without any prior notice. maybe this is what you experienced?

 

[JeremyNH]

Well I think maybe I found the issue.

Today while dropping my dogs off at daycare (my dads house) I let the truck idle. I talked to him for probably 10 minutes. When I got back in the truck it was hotter than the depths of hell!

The only real difference I can think of is the radiator. I replaced it a while ago with a all alluminum one that may also be a little bigger than stock? I don’t remember. Anyway i think that the truck is just running cool. I know it could be a thermostat issue but my temps don’t say there is a issue. It runs about 186-188 going down the highway in the winter and when I got in the cab after idling it was 194 according to my scangauge.

I may try putting some cardboard in the grille if we keep getting cold temps but it should start warming up now. I don’t think it’s going to stop working on me

You said in your first post that the inlet hose was too hot to hold and the outlet merely warm despite only moderate heat loss to the cab. To me that sounds like poor flow through the heater core. I know that heaters tend to be a repository for crud which is why it's important to flush the core when doing a coolant flush. It may be you had some blockage that finally cleared now that you are sending more coolant through it with the heating season. Maybe think about a flush in the Spring.

I have a 1998 5.7L that had a failed blend door three years ago (took the old one apart just to be sure and it had a cracked plastic gear, the Dorman replacements looks to use nylon gears so won't break, and the seemingly metal on the gear is only on the journal the internals are all azure blue plastic). You have to dismount the dash to get that sob out. Nice that you avoided that fun.